U.S. Marine veteran Jon Hammar spends most of his day on a bunk bed in a dingy Mexican prison, and at times his ankle is restrained by a handcuff locked to a bed.

Hammar, 27, is charged with illegal possession of a firearm – an heirloom shotgun that once belonged to his grandfather – and has spent more than four months in a prison in Matamoros, Mexico.

The saga of Hammar, a veteran of Marine campaigns in Iraq and Afghanistan, was first revealed by McClatchy on Dec. 6 and has become a pre-Christmas bilateral issue brought up on the floors of the U.S. Senate and the House of Representatives.

For the first time, a photo of Hammar’s detention has been made public. Olivia Hammar, a magazine publisher who is the detained Marine veteran’s mother, said an anonymous sympathizer sent her the photograph from a Mexican Yahoo account with a short message in Spanish.

It said in part: “I have not given my name because I like my job and do not want to lose it. Juan (Jon) is fine but I hope he gets out soon.”

The photo shows Hammar sitting on a metal bunk bed. A thin foam mattress covers the bed. A bearded Hammar, sitting shirtless and showing tattoos on his right shoulder and left forearm, looks at the camera.

The wall behind him has much of the paint flecked off, and the grimy concrete floor conveys the grunginess of the setting.

Hammar’s father visited him in the jail Sept. 14, and his mother says she believes the photo definitely was taken at the jail.

The date of the photo is not known. A spokesman for the State Department, William Ostick, said last week that the department believed guards at the prison had stopped restraining Hammar with a chain.

Reiterating that assertion Monday, another State Department spokesperson, Ariel Vaagen, said in an email: “When we learned that physical restraints were being used, we raised the issue with prison authorities, who agreed to stop using the restraints. Mr. Hammar is not being restrained in any way, and has not been since consular officers intervened.”

Vaagen said consular officers had visited Hammar four times in the prison, most recently on Nov. 29 and Dec. 13.

Rep. Ileana Ros-Lehtinen, a Florida Republican whose district includes the Hammar family home in Palmetto Bay, southwest of Miami, offered a different story Friday on “The O’Reilly Factor,” a Fox News Channel television show. She noted that Hammar was removed from the general prison population shortly after his arrest in mid-August to an area away from hardened gangsters but less well guarded.

“In that area that is less secure, it is so unsecure that they fear that he will escape and in order to overcome that fear, they have chained him to his bed,” Ros-Lehtinen said. She added that Mexico’s ambassador to the United States, Arturo Sarukhan, told her Hammar still was being restrained.

Hammar was honorably discharged by the Marines in 2007 and remained in inactive reserve for another four years. He suffered from post-traumatic stress disorder and voluntarily checked into a rehabilitation center in California’s Napa Valley for nine months, leaving in May.

A passionate surfer, he and a fellow Marine veteran bought a used motor home over the summer and started heading from the Miami area toward the Mexican border, bound for the beaches of Costa Rica.

Hammar carried a .410-bore Sears & Roebuck shotgun that had been in his family for decades. His family said U.S. Border and Customs Protection agents in Brownsville, Texas, asked him to fill out a registration form for the shotgun and indicated it would be no problem to carry it into Mexico.

Mexican authorities immediately threw Hammar into a state prison, where fellow inmates belonging to Los Zetas, a feared organized crime group, sought to extort money from his family, saying that if they didn’t pay Hammar would be killed.

At that point, pleas by the family to U.S. diplomats at a consulate in Matamoros succeeded in helping get Hammar moved to a storage area of the prison near a guard station. That is where the photo was taken, his mother said.

Publicity over Hammar’s situation has drawn concern from officials and business owners in Tamaulipas, the border state in which Matamoros is located. On Thursday, Gerardo Acevedo Danache, vice president of the state’s chamber of commerce, called on President Enrique Pena Nieto and state Gov. Egidio Torre Cantu to pardon Hammar.

“With this detention and all the publicity around it, Mexico, Tamaulipas and Matamoros send a very bad signal to the tourists who visit us,” Acevedo said in a news conference.

At most border crossings into Mexico, signs warn Americans against carrying firearms and ammunition.

The State Department’s Vaagen said Hammar would have needed to get permission from a Mexican consulate within the United States prior to crossing into the nation with a firearm.

“The U.S. Department of State’s Consular Specific Information for Mexico clearly states that no one should take firearms into Mexico without first obtaining a proper permit from the Mexican embassy or one of its consulates,” Vaagen wrote. “There are also clear signs above the roads on the approaches to land border crossings warning travelers to not take firearms or ammunition into Mexico.”

Hammar’s plight has touched fellow Marines with whom he served in Iraq and Afghanistan, and they have been among those who have launched a petition campaign at the White House seeking his freedom. As of Monday morning, 17,200 people had signed the online petition.

McClatchy Washington Bureau Chief James Asher contributed to this report.